MRI - The patient lies on a stretcher that is moved into a cylinder containing a magnetic field (the MRI scanner). A special coil is placed over the knee to improve the quality of the images. Earplugs are worn to muffle the loud thumping sound produced by electrical switching of the magnetic fields during the imaging. A contrast agent called gadolinium is injected through a catheter into a vein to improve the quality of the images. An intercom system permits the patient to communicate with the technician at all times during the procedure.